1. Field of the Invention.
This invention is directed to power supplies, in general, and to a miniaturized power supply which has low voltage and low ripple, in particular.
2. Prior Art.
There are many power supplies which are known in the prior art. However, there are not many power supplies known in the art which use the switching mode of operation and which can operate at high frequencies, for example, on the order of 1 MHz. Moreover, in the current technology the trend is to produce power supplies which have lower and lower output voltage while producing higher and higher currents. These operating requirements tend to make power supply design and production very difficult.
In known power supplies, those using the "fly back" technique generally require relatively few components. This is because the fly-back type power supplies, generally, tend to perform some of the filtering and/or storage capability within the transformer of the power supply.
In power supplies other than the fly back type, such as the forward converter (wherein the transformer is used for isolation) or the step-up or step-down type, another inductor element is usually required in the low pass filter element in order to filter the ripple on the output signal. Thus, this configuration requires a minimum of two inductors in every power supply.
Inasmuch as the inductive elements tend to comprise the vast majority of the structural volume and weight in the power supplies of known design, any additional inductors are usually undesirable components. Therefore, it is desirable to devise a power supply which can provide a lower output voltage (e.g. 5v) and a higher output current (e.g. up to 1OOA) while reducing the physical size requirements of the magnetic (inductive) components.
Also, in the known prior art, it is typical to include a capacitive output load in order to provide desirable filtering of the output signal. However, this output capacitance places certain requirements and restrictions on the circuit design. These ratings are especially critical in many military applications.
Moreover, in the known circuit topologies, it is desirable to use ceramic dielectric filter capacitors, especially in higher frequency applications. This construction is difficult to achieve in a relatively simple, inexpensive fashion which is also acceptable in this circuit configuration. That is, the high frequency, low voltage output signal requires a relatively large capacitor which is difficult (or cumbersome) to provide.